Water is integral to an oil sands processing operation because it facilitates the transfer and/or separation of mined material. Constituents of the mined material include hydrocarbon (sometimes referred to as bitumen), sand, clay, and water. The most common process to extract the hydrocarbon from the mixture involves crushing the mined material and later suspending the material in water, typically with the addition of heat, to form a slurry. The resultant slurry is processed, for example, by using froth flotation via the addition of chemicals to the slurry. This promotes the formation of a stable froth containing the hydrocarbon and the separation of the hydrocarbon from the other constituents.
Large amounts of water are required to facilitate the above separation process. The resultant stream, which contains the unwanted constituents, is sent to a tailings settling pond to allow the sand, clay, and other particulate(s) to settle.
Environmental concerns coupled with the large amounts of water involved make it mandatory to return much, if not all, of the water to the process. The return of water to an oil sands process, which contains unwanted constituents, can impair the oil sands process operation. Potential problems include, but are not limited to, erosion of pumps and piping from entrained particles, and loss in hydrocarbon separation efficiency from accumulation of fine particles, etc. An additional problem derives from the discharge of pond water when a mine is closed. When this occurs, local water quality permit obligations may require removal of unsettled or colloidal particles from the pond water.
Reclamation of tailings pond water for process reuse and other uses, especially back into an oil sands process, is an industry focus. Purifying the water through membrane separation systems is problematic because the process water from oil sands has large amounts of hydrocarbons and particulate matter. The water makeup creates a prime environment for fouling of membranes and subsequent reduction in water flux through the membranes.
Fouling of membranes and reducing flux through membranes makes the processing of water for reuse in an oil sands process less efficient. More specifically, when the membrane fouls, it is less efficient in that it requires more frequent cleaning and possible replacement. In addition, it also takes more energy and time for filtering when membranes foul, and the pond water passes through a membrane at a slower rate.
Therefore, a more efficacious method of enhancing flux of pond water from oil sands through a membrane separation system and purifying the process water is desired.